Catalytic heater

ABSTRACT

A heater device for preheating liquid coolant of an internal combustion engine having an elongate cylindrical heat exchanger with an elongate catalytic heater assembly releasably mounted generally coaxially therein. The heater assembly has a catalytic impregnated fibrous material wrapped around an elongate porous ceramic tube with closed ends and an injector which discharges vaporized fuel into the interior of the ceramic tube.

United States Patent Charboneau et a]. Oct. 14, 1975 54] CATALYTIC HEATER 3,277,886 10/1966 Ryals 6:31. 126/350 A 3,501,257 3/1970 Hilton ct al.... [75] Inventors: Benny Qty; 3,807,939 4 1974 Carlsson 431 170 Paul I. Nielsen, Unionvllle, both of I Mlch' Primary ExaminerEdward G. Favors [73] Assignee; Walbro Corporation, Cass City Attorney, Agent, or FirmBarnes, Kisselle, Raisch & Mich. Choate [22] Filed: July 31, 1974 ABSTRACT pp NOJ 493,709 A heater device for preheating liquid coolant of an internal combustion engine having an elongate cylindri- 52 us. (:1 126/350 A; 431/170; 431/208 Cal heat exchanger with an elongate catalytic heater 51 Int. c1. F24H 1/00 assembly releasably mounted generally coaxially 58 Field of Search 431/170, 7,208; therein The heater assembly has a catalytic p 126/350 A 9 RC nated fibrous material wrapped around an elongate porous ceramic tube with closed ends and an injector 56] References Cited which discharges vaporized fuel into the interior of the ceramic tube.

22 Claims, 11 Drawing Figures US. Patent Oct. 14,1975 Sheet10f6 3,911,896

US. Patent Oct. 14, 1975 Sheet 2 of6 3,911,896

US. Patent Oct. 14, 1975 Sheet4of6 3,911,896

US. Patent Oct. 14, 1975 Sheet5of6 3,911,896

US. Patent Oct.14,1975 Sheet60f6 3,911,896

CATALYTIC HEATER This invention relates to a device for preheating the liquid coolant of an internal combustion engine and more particularly to such a device with a flameless catalytic heater.

Objects of this invention are to provide a catalytic heater device which is safe, compact, of economical manufacture and assembly, and has a long maintenance-free service life.

These and other objects, features, and advantages of this invention will be apparent from the following description, appended claims, and accompanying drawings in which:

FIG. 1 is a side view partially in section of a catalytic heater embodying this invention;

FIG. 2 is a top view of the catalytic heater of FIG. 1; FIG. 3 is a bottom view of the catalytic heater of FIG.

FIG. 4 is a fragmentary sectional view on line 44 of FIG. 2;

FIG. 5 is a fragmentary view on line 5-5 of FIG. 3;

FIG. 6 is a semi-diagrammatic view of the catalytic heater of FIG. 1 connected to both a control box and a fuel pump connected to the gasoline line of a moter vehicle;

FIG. 7 is a schematic diagram of the electric control circuit for both the catalytic heater and fuel pump of FIG. 6;

FIG. 8 is a side view partially in section of a modified catalytic heater embodying this invention;

FIG. 9 is a semi-diagrammatic view of the catalytic heater of FIG. 8 connected to both a control box and a fuel pump connected to the gasoline line of a motor vehicle;

FIG. 10 is a schematic diagram of an electronic control circuit for the catalytic heater and fuel pump of FIG. 8; and

FIG. 11 is a sectional view of the fuel pump of FIGS. 6 and 9.

Referring in more detail to the drawings, FIG. 1 illustrates a catalytic heater 10 embodying this invention having a heat exchanger jacket 12 encircling a catalytic heater assembly 14. Heat exchanger 12 has a cylindrical chamber 16 defined by an inner metallic tube 18, an outer metallic tube 20 encircling the inner tube, and metallic end rings 22 interposed between the tubes and fixed thereto, such as by brazing. Engine liquid coolant enters chamber 16 through an inlet conduit 28 fixed to ,outer tube 20 adjacent the lower end of chamber 16 and flows from chamber 16 through an outlet conduit 30 fixed to outer tube 20 adjacent the upper end of chamber 16. A check valve 32 in inlet conduit 28 prevents liquid coolant from flowing out of chamber 16 through the inlet conduit. A plurality of slots or windows 34 and 36 adjacent opposed ends of inner tube 18 allows atmospheric air to flow through the tube adjacent the outer periphery of heater assembly 14.

As shown in FIGS. 1 and 4, heater assembly 14 has a porous ceramic tube 38 with upper and lower end caps 40 and 42 fixed thereto. A layer of a fibrous material 44 is wrapped around ceramic tube 38 and impregnated with a catalytic agent, such as platinum. A suitable fibrous material is the ceramic felt T-3 fiber produced by Refractory Products Company of Carentersville, III. A nichrome wire 46 extends axially along the outside of tube 38 beneath the layer of fibrous material 44 to provide an electrical resistance heating element for preheating the catalytic heater assembly. One end of nichrome wire 46 is connected to an insulated binding post 48 mounted on tube 18 and the other end of wire 46 is connected to tube 18 and a ground lead wire 50 by a machine screw 52.

Upper end cap 40 of heater assembly 14 has a central depression or cup 54 therein which extends into the interior of the upper end of ceramic tube 38. A temperature responsive or thermostatic switch 56 with insulated lead wires 58 and 60 connected thereto is potted in the cup 54 of end cap 40 by a suitable potting material 56, such as Acid-Alk Mortar No. 33 available from Sauereisen Cements Company of Pittsburgh, Pa. A fuel injector 62 with a union 64 on the lower end of an evaporator tube 66 extends through and is fixed to lower end cap 42 of heater assembly 14 to discharge vaporized fuel into the interior of ceramic tube 38 adjacent the longitudinal mid portion thereof.

Heater assembly 14 is mounted substantially coaxially in inner metallic tube 18 by an upper locator disc 67 and a lower locator disc 68. As shown in FIGS. 1 and 2, upper locator disc 67 bears on the upper end of heater assembly 14 and has three circumferentially spaced, inwardly and downwardly struck tabs 70, which engage the outer periphery of upper end cap 40, and a central aperture 72 providing clearance for thermostatic switch 56. Locator disc 67 abuts on three circumferentially spaced, inwardly struck tabs 74 in the upper end of inner tube 18. As shown in FIG. 1, heater assembly 14 is yieldably urged into engagement with upper locator disc 67 by a spring 76 interposed between and bearing on lower locator disc 68 and lower end cap 42 of the heater assembly. As shown in FIGS. 1, 3 and 5, lower locator disc 68 is releasably retained in tube 18 by three circumferentially spaced tabs 78 on the disc 68 which are received in three circumferentially spaced reentrant slots 80 in the lower end of tube 18. Rotating of lower disc 68 for installation in and removal from tube 18 is facilitated by a pair of holes 81 in the disc 68. A rubber grommet 82 encircles injector 62 and is received in an aperture 84 in locator disc 68 to coaxially position the lower end of heater assembly 14 in tube 18.

When catalytic heater 10 is installed to preheat the liquid coolant of an internal combustion engine, fuel injector 62 is connected to a source of pressurized hydrocarbon fuel, such as gasoline or liquified petroleum gas. As shown in FIG. 6, when device 10 is installed in a motor vehicle, gasoline may be supplied to injector 62 under pressure by a separate electric fuel pump 84 with an inlet connected by a line 86 through a tee 88 to the fuel line 90 of the vehicle (not shown) between the gasoline tank and the fuel pump of the internal combustion engine. The outlet of pump 84 is connected to injector 62 through a fuel metering orifice 92, lines 94 and 96, and male coupling 98. As indicated by arrow (FIGS. 1 and 6), catalytic heater 10 should be mounted so that the longitudinal axis of heater assembly 14 extends generally vertically with fuel injector 62 at the lower end thereof. The catalytic heater 10 is mounted at a vertical height between the vertically highest and lowest pointsin the cooling system of the engine and preferably closer to the highest point thereof so that the liquid coolant will be circulated through the heater and engine when the heater is operating. The inlet conduit 28 of heat exchanger 12 is connected by a hose 102 to the engine cooling system at a low point thereof such as the engine drain opening or through a core plug in the side of the block of the engine. The outlet conduit 30 of heat exchanger 12 is connected by a hose 104 to the engine cooling system at a higher point than the inlet 28 such as at the connection at the heater inlet hose to the cooling system of the vehicle.

As shown in FIGS. 6 and 7, control box 106 is electrically connected to catalytic heater to control the functioning thereof. Control box 106 has a front panel 108 with a master power switch 110 mounted thereon and a timer switch 112 mounted therein with a manually movable actuator lever 114 which projects through a slot 116 in control panel 108. One contact of power switch 110 is connected through a lead line 118 to the positive pole of a battery 120 and the negative pole of the battery is connected to ground of the vehicle frame by a lead line 122. The other contact of switch 110 is connected to both one contact of switch 112 by a lead line 124 and to one contact of temperature responsive switch 56 by lead line 60. The other contact of temperature responsive switch 56 is connected by lead line 58 to the solenoid actuating coil 126 of electric fuel pump 84 which is grounded by a lead line 127. The other contact of timer switch 112 is connected by a lead line 128 to one end of nichrome wire resistance heating element 46 through binding post 48 and the other end of the nichrome wire 46 is grounded through lead line 50.

In using catalytic heater 10 to preheat the engine coolant of an internal combustion engine, master power switch 110 and timer switch 112 are both closed to supply current through lead line 128 to the nichrome wire electrical resistance heating element 46. Heating element 46 preheats at least portions of the catalytic agent of heater assembly 14 to an operating temperature which would produce a catalytic heat reaction with fuel discharged into the heater assembly. Timer switch 112 controls the length of time current is supplied to heating element 46 and turns the heating element off after sufficient time has elapsed for the catalytic agent to be heated to an operating temperature. Temperature responsive switch 56 closes in response to the preheating of the catalytic agent to its operating temperature to supply current through lead lines 60 and 58 to energize electric fuel pump 84. When fuel pump 84 is energized, it supplies gasoline under pressure to fuel injector 62. The gasoline is metered into injector 62 by orifices 92, becomes vaporized as it passes upwardly through evaporator tube 66, and is discharged into the interior of ceramic tube 38. Under the influence of the catalytic agent of the heater assembly, the vaporized fuel undergoes a catalytic reaction producing heat which warms liquid coolant in heat exchanger 12. Heating of the liquid coolant in chamber 16 of heat exchanger 12 produces a thermosiphon action which causes warmer liquid to flow out of the heat exchanger through outlet conduit and into the cooling system of the engine, and cooler liquid from the engine cooling system enters the bottom of the heat exchanger through inlet conduit 28. This preheats the liquid coolant of the internal combustion engine, and hence, the engine itself which greatly facilitates starting of the engine in cold weather conditions.

FIG. 8 illustrates a modified catalytic heater 10 embodying this invention in which like numerals designate component parts which are the same as the corresponding component parts of catalytic heater 10. The catalytic heater assembly 14' of heater 10' has a pair of ceramic end caps 130 received on opposed ends of heater assembly 14 and is centered in heat exchanger 5 jacket 12 by discs 67 and 68. Thermostatic switch 56 is secured to the upper end cup by a suitable potting material, such as the Leepoxy Epoxy System No. 16-149 available from Leepoxy Plastics, Inc. of Fort Wayne, Ind. Liquid hydrocarbon fuels, such as gasoline, are at least partially vaporized and discharged within catalytic heater assembly 14' by a fuel injector 132 which has an evaporator tube 134 with a tube screen 135 and a union 136 at the upper end thereof. Evaporator tube 134 is fixed to disc 67' with the lower portion thereof extending coaxially into heater assembly 14' through apertures in upper end plate 40' and cup 130. To prevent high winds from extinguishing the catalytic reaction of fuel with heater element 14, a tubular shield 138 on the upper end of heat exchanger 12 extends substantially above exhaust or outlet ports 36. Shield 138 is received over the upper end of outer tube 20 of heat exchanger 12 and retained thereon by a band or hose clamp 140. If desired, tubular shield 138 could be simply an extension of outer tube 20 of heat exchanger 12.

To receive and vaporize any liquid fuel dischargedfrom fuel injector 132, a secondary evaporator assembly 142 is coaxially received in the lower end of heater assembly 14'. Evaporator assembly 142 has an evaporator tube 144 into which droplets of fuel discharged from tube 134 are funneled by a flared upper end 146. Evaporator tube 144 is fixed to lower end cap 42 of heater assembly 14', extends through lower end cup 130, and is closed at the lower end thereof by a plug 148 received in a union 150 fixed thereto. I

Catalytic heater 10' is supplied with a pressurized hydrocarbon fuel in gaseous or liquid form, such as liqui fied petroleum gas or gasoline. Gaseous fuels are supplied to catalytic heater 10' through secondary evaporator assembly 142 by connecting a suitable conduit to union 150 thereof with the injector 132 being sealed by inserting plug 148 in union 136 thereof. Liquid fuels are supplied to catalytic heater 10' through injector 132 by a suitable conduit connected to union 136 thereof and the lower end of the secondary evaporator is sealed by inserting plug 148 in union 150 thereof.

.As' shown in FIG. 9, when catalytic heater 10' is installed in an automotive vehicle, gasoline may be supplied under pressure to injector 132 by a separate electric fuel pump 84 with an inlet connected by line 86 through tee 88 to fuel line 90 of the vehicle (not shown) between the gasoline tank and the fuel pump of the internal combustion engine of the vehicle. The out let of pump 84 is connected to injector 132 through a line 154 and union 136. As indicated by arrow 100, catalyn'c heater 10 is mounted so that the longitudinal axis of the heater assembly 14' extends generally vertically with fuel injector 132 at the upper end thereof. Catalytic heater 10' is connected by hoses 102 and 104 to the cooling system of the engine and mounted at a vertical height in relation thereto in the same manner as catalytic heater 10 to produce a thermosiphon action to circulate coolant to the catalytic heater and the cooling system.

A control box 156 with an electronic circuit 158 shown schematically in FIG. 10 cycles catalytic heater l0 and fuel pump 84. Power is supplied to a DC power bus 160 of control circuit 158 from battery 120 through a fuse 162 and a master power switch 164 with an indicator light 166 connected by lead lines 168, 169 and 170.

Circuit 158 has a preheat control section 172 which is responsive to application of battery power to bus 160 to apply power to heating element 46 for a predetermined time interval to preheat the catalyst of heater assembly 14'. Control section 172 comprises a comparator 174 having a reference input 176 connected through a resistor 178 to bus 160, and having a threshold input 180 connected through a resistor 182 to bus 160 and through a capacitor 184 to ground 186 of the vehicle frame. A latch 188 receivesa first input 190 from the output 192 of comparator 174, and a second input 194 from bus 160 directly. Latch 188 has an output 196 connected through the anode-cathode junction of a silicon diode 198 and thence through a coil 200 of a relay 202 to ground 186. A second diode 204 is con nected in reverse polarity across coil 200 to suppress inductive ringing in the coil when relay 202 turns off. Relay 202 also has a pair of normally open contacts 206, 208 connected to bus 160 and preheat element 46, and responsive to energization of coil 200 to apply battery power directly to heating element 46.

In the operation of preheat control section 172, the output of latch 188 is initially set to a high voltage state by application of battery power to bus 160. This relatively high voltage forward biases diode 198 so that relay 202 is energized and preheat current is supplied to element 46. At the same time current flows through resistor 182 and into capacitor 184 so that a charge is gradually built up thereupon. After an interval of time determined by the values of resistor 182 and capacitor 184, the voltage on the capacitor at threshold input 180 of comparator 174 exceeds the reference voltage at input 176 so that the comparator provides a reset signal at input 190 of latch 188. The latch is thus reset so that the output thereof goes low and relay 202 is deenergized until master switch 164 is turned off and then on again to reset latch 188 to a high voltage state. The preheat time interval determined by resistor 182 and capacitor 184 is preferably in the range of twelve to fourteen minutes.

Control circuit 158 further comprises a pump control section 210 which includes a first comparator 212 having its reference input 214 connected through a resistor 216 to bus 160, and through series connected resistors 218, 220 to ground 186 of the vehicle frame. A filter capacitor 230 is connected across resistor 220. The

threshold input 232 of comparator 212 is connected through series connected resistors 232, 236 to bus 160, and through a capacitor'238 to ground 186. A second comparator 240 has its threshold input 242 connected to threshold input 232 of comparator 212, and has its reference input 244 connected to the junction of resistors 218, 220. Resistors 216, 218 and 220 thus form a voltage divider which places a first reference voltage at reference input 214 of comparator 212, and a second lower reference voltage at the reference input 244 of comparator 240. A resistor 222 and a normally open pushbutton switch 228 are connected in series across resistor 236. Switch 228 is mounted on control box 156 and may be manually activated to prime pump 84 as explained in detail hereinafter.

A latch 246 has a first input 248 connected to the output 250 of comparator 212, and has a second input 252 connected to the output 254 of comparator 240. The output 256 of latch 246 is connected through a resistor 258 to the base of a PNP transistor 260 which has its emitter connected to bus 160 and its collector connected through the solenoid coil 126 of pump 84 to ground 186. A diode 262 is connected in reverse polarity across coil 126 to suppress inductive ringing in the coil when transistor 260 turns off. Output 256 of latch 246 is also connected through a resistor 272 to input 176 of comparator 174, and to a first input 264 of a discharge switch 266 which has a second input 268 connected to the junction of resistors 234, 246 and an output 270 connected to ground 186.

In the operation of pump control section 210, output 256 of latch 246 is set high when battery power is initially applied to bus 160 so that the emitter-base junction of transistor 260 is reverse biased and current is blocked from coil 126 of pump 84. In the meantime current passes through resistors 236, 234 into capacitor 238 so that the voltage at threshold input 232 of comparator 212 gradually rises. When this rising voltage exceeds the reference voltage supplied at input 214 by voltage divider 216, 218, 220, comparator 212 supplies a reset input to latch 246 so that output 256 goes low, transistor 260 conducts and current is supplied to coil 126 of pump 84. At the same time, input 264 of discharge switch 266 goes low so that switch 266 discharges capacitor 238 through resistor 234 and discharge switch input 268 to ground 186. When the decreasing voltage on capacitor 238 at threshold input 242 of comparator 240 drops below the level of the second lower reference voltage supplied at reference input 244 by voltage divider 216, 218, 220, comparator 240 provides a set signal at input 252 of latch 246 so that the output thereof goes high thus turning off transistor 260 and blocking current flow to coil 126 of pump 84. Discharge switch 266 is also turned off at this time so that capacitor 238 may recharge. Thus, pump control circuit 210 operates as an oscillator which has a period and duty cycle dependent upon the relative values of resistors 216, 218, 220, 234, 236 and capacitor 238. In the preferred embodiment of catalytic heater 10' the charge time of capacitor 238 through resistors 236, 234 may be in the range of 5 to 15 seconds and preferably is about 10 seconds while the discharge time thereof through resistor 234 and switch 266 may be in the range of 30 to milliseconds and preferably is about 50 to 60 milliseconds. Thus, current is supplied to coil 126 of pump 84 preferably for 50 to 60 milliseconds at IO-second intervals.

To prime fuel pump 84 a switch 228 is closed to place resistor 222 in parallel with resistor 236, thereby decreasing the charge time for capacitor 238 and increasing the rate at which pump 84 is cycled. The decreased charge time for capacitor 238 when control section 210 is operating in the pump-priming mode may be in the range of within 200 to 700 milliseconds and is preferably about 400 to 500 milliseconds.

Control circuit 158 also includes a pump inhibit circuit-274 which is responsive to the temperature of catalytic heater assembly 14' to selectively inhibit activation of pump control section 210 if heater device 10' is not functioning properly. Circuit 274 includes a first NPN transistor 276 which has its base connected through a resistor 278 to the cathode of diode 198, and its emitter connected directly to ground 186. The collector of transistor 276 is connected through a resistor 280 to bus 160, and to the base of a second NPN tran sistor 282. The base of transistor 282 is also connected to ground 186 through normally open thermal switch 56 which is mounted on heater assembly 14 and responsive to the temperature thereof to connect the base of transistor 282 directly to ground. The emitter of transistor 282 is connected to ground and the collector thereof is connected to the junction of resistor 234 and capacitor 238. Thus, when latch 188 supplies preheat current to element 46, transistor 276 is turned on and transistor 282 is turned off so that capacitor 238 is allowed to alternately charge and discharge as described above. If heater 10' is operating properly, catalytic heater assembly 14' will be preheated to a temperature at which thermal switch 56 closes and the base of transistor 282 is connected to ground independently of preheat section 172 before the preheat section 172 turns off. However, if the temperature of heater assembly 14' is below the temperature at which switch 56 closes when preheat section 172 turns off, or if the heater assembly temperature should thereafter fall below such predetermined temperature, switch 56 will open and current will be supplied to the base emitter junction of transistor 282 through resistor 280. Transistor 282 will then be turned on to drain substantially all of the charge from capacitor 238, and to thereby inhibit further operation of pump control section 210 and hence pump 84.

In using catalytic heater 10' to preheat the engine coolant of an internal combustion engine, master switch 162 is manually actuated to energize control circuit 158 to supply current to resistance heating element 46. Heating element'46 preheats at least portions of the catalytic agent of heater assembly 14' to an operating temperature which would produce a catalytic heat reaction with fuel discharged into the heater assembly. The preheat control section 172 of circuit 158 controls the length of time current is supplied to heating element 46 and turns the heating element off after sufficient time has elapsed for at least portions of the catalytic agent to be heated to an operating temperature. Prior to the heating element being turned off by control section 172, fuel pump 84 is energized to discharge fuel through injector 132 into heating element '14 by the pump control section 210 of control circuit 158 and, if catalytic heater 10' is functioning properly, temperature responsive switch 56 closes to assure continued cycling of pump 84 to supply fuel to the catalytic heater. The cyclic or pulsating flow of liquid fuel supplied by pump 84 to injector 132 is smoothed or evened out by fuel screen 135, at least partially vaporized by evaporator tube 134 and discharged therefrom into heater assembly 14'. The vaporized portion of the fuel under the influence of the catalytic agent of heater assembly 14 undergoes a catalytic reaction producing heat which warms liquid coolant in heat exchanger 12. If the fuel is not completely vaporized by evaporator tube 134, the liquid portion thereof will drop by gravity into secondary evaporator assembly 142 into which it will be subsequently vaporized and discharged into the interior of heater assembly 14' to undergo a catalytic reaction producing heat to warm the liquid coolant in heat exchanger 12. Liquid fuel is vaporized in secondary evaporator assembly 142 because evaporator tube 144 is maintained at an elevated temperature by the heat produced by the catalytic reaction. Heating of the liquid coolant in heat exchanger 12 produces a thermosiphon action to circulate the liquid coolant of the engine and thus preheat the engine in the same manner as catalytic heater 10.

The useful life of the catalytic agent of the catalytic heaters is belived to be substantially decreased by contact of the catalytic agent with liquid fuel, and hence, no fuel should be supplied to the catalytic heaters when they are not being operated. However, it has been discovered that the main fuel pump of at leat some internal combustion engines creates sufficient pressure surges or pulses in fuel line 90 to force fuel through conventional electric fuel pumps utilized with the catalytic heaters and thence into the catalytic heaters when they are not operating, thereby decreasing the useful life of the catalytic agent thereof. This may be prevented from happening by using conventional valves with a conventional electric pump supplying fuel to the catalytic heaters by arranging the valves to prevent fuel from flowing through the conventional pump when the catalytic heater is not operating. However, it is preferred to use a specially designed pump, such as pump 84, with a suitable valve arrangement incorporated directly therein.

As shown in FIG. 1 1, pump 84 has a housing 290 with a flexible diaphragm 292 received therein and underlying a pump chamber 294 in a carrier plate 296 fixed in the housing. Gasoline is admitted to pump chamber 294 through inlet conduit 298, inlet valve assembly 300, and passageway 302 through carrier plate 296 and discharged from the pump chamber through outlet passageway 304 in carrier plate 296, output valve assembly 306 and outlet conduit 308. The gasoline is moved through pump chamber 294 by the flexing of diaphragm 292 which is actuated by an armature 310 connected thereto, yieldably biased in one direction by a spring 312, and moved in the opposite direction by energization of solenoid coil 126. The length of the stroke of armature 310 and hence the quantity of fuel delivered on each discharge stroke of pump 84 is controlled by adjustment of a threaded stop screw 314 received in a nut 316 fixed to housing 290.

Gasoline is prevented from flowing through pump 84 when solenoid coil 126 is de-energized by a valve assembly 318 mounted on carrier plate 296 and shown in FIG. 11 in the open position with coil 126 energized. Valve assembly 318 has a valve 320 with a bulbous stem 322 received for reciprocation in a counterbore 324 in carrier plate 296 to close and open (as shown in FIG. 11) fuel outlet passage 304. Valve 318 has a metallic wear cap 326 on the lower surface thereof and is yieldably biased by a spring 328 into engagement with armature 310 for reciprocation therewith.

In operation of pump 84 energization of coil 126 moves armature 310 to the position shown in FIG. 11, thereby opening valve 316 and flexing diaphragm 292 to pull gasoline into pump chamber 294 through inlet conduit 298, inlet valve 300 and passageway 302. When coil 126 is de-energized, spring 312 moves armature 310 upwardly from the position shown in FIG. 1 1, thereby moving diaphragm 292 to discharge fuel from pump chamber 294 through passageway 304, outlet valve 306 and outlet conduit 308, and, upon completion of the discharge stroke of diaphragm 292, closing valve 320 against the bias of spring 324. Thus, valve 320 remains closed so long as coil 126 is de-energized, thereby preventing gasoline from being forced through pump 84 when the pump is not operating by pressure surges or pulses in the fuel line 90 to which inlet conduit 298 is connected.

Since the useful life of the catalytic agent is decreased by contact with liquid fuel, the quantity of liquid fuel supplied to catalytic heaters 10 and 10' during operation thereof should be controlled within close tolerances to assure that an excess quantity of liquid fuel is not supplied to the catalytic heaters. The quantity of liquid fuel supplied to heater 10 is controlled by adjustment of stop screw 314 of pump 84 and metering orifree 92 and the quantity of liquid fuel supplied to catalytic heater 10 is controlled by adjustment of stop screw 314 of pump 84 and the rate of cycling of fuel pump 84 by pump control section 210 of control circuit 158. Preferably, catalytic heater 10, rather than heater 10, is used with liquid fuels since the secondary evaporator assembly thereof prevents liquid fuel from coming in contact with the catalytic agent.

A heater assembly embodying this invention in which vaporized fuel is discharged into a closed elongate porous chamber extending generally vertically with a catalytic agent distributed about the outer periphery thereof provides a flameless catalytic heater for an internal combustion engine which will operate safely and efficiently, has a long service life and requires little or no maintenance. The useful life of the catalytic agent of the heater device is prolonged when used with liquid fuels by an evaporator received in the lower end of the closed chamber with the fuel injector overlying the evaporator. The arrangement of an elongate catalytic heater assembly within a cylindrical heat exchanger provides a compact heater device embodying this invention. The releasable mounting of the heater assembly within an elongate tube which is a wall of the heat exchanger provides a catalytic heater of economical manufacture and assembly and facilitates removal of the heater assembly for inspection, repair, or replacement after the catalytic heater has been installed for use with an internal combustion engine.

We claim:

1. A flameless heater using a combustible hydrocarbon fuel for preheating liquid coolant of an internal combustion engine comprising; an elongate, cylindrically shaped heat exchanger having an inlet and an outlet for liquid coolant of an engine, said heat exchanger being adapted to be mounted with its axis extending generally vertically, an elongate catalytic heater assembly received in said cylindrically shaped heat exchanger, said catalytic heater assembly comprising an elongate porous tube, end caps closing both ends of said porous tube, a layer of fibrous material overlying said porous tube and being impregnated with a catalytic material, an electric resistance heater element carried by said porous tube for preheating said catalytic material, and a fuel injector extending into said porous tube for discharging at least partially vaporized hydrocarbon fuel into the interior of said porous tube, whereby when a vaporized hydrocarbon fuel is discharged by said injector into said catalytic heater assembly when preheated by said electric resistance element, the fuel is oxidized by a flameless catalytic reaction to heat liquid coolant of the engine in the heat exchanger.

2. The flameless heater of claim 1 which also comprises a temperature responsive switch mounted on one of said end caps.

3. The flameless heater of claim 1 wherein said injector extends through one of said end caps and comprises an evaporator tube adapted to discharge at least partially vaporized hydrocarbon fuel into the interior of said tube adjacent the mid portion of the longitude of said porous tube.

4. The flameless heater of claim 2 wherein said injector extends through one of said end caps and comprises an evaporator tube adapted to discharge at least partially vaporized hydrocarbon fuel into the interior of said porous tube adjacent the mid portion of the longitude of said porous tube.

5. The flameless heater of claim 1 which comprises an elongate metallic tube having an axial length exceeding the axial length of said porous tube of said heater assembly and an inside diameter exceeding the outside diameter of said heater assembly, locators received in said metallic tube adjacent opposed ends of said heater assembly to position said heater assembly generally coaxially with metallic tube.

6. The flameless heater of claim 5 wherein said metallic tube is a wall of said heat exchanger which is in contact with liquid coolant in said heat exchanger.

7. The flameless heater of claim 5 wherein said locators comprise discs and which also comprises abutments on said metallic tube engageable with one of said discs to limit movement of said one disc generally axially through said metallic tube in at least one direction, said one disc bearing on said heater assembly adjacent one end thereof, and a spring interposed between said other disc and said heater assembly to urge said one disc into engagement with both said abutment and said heater assembly.

8. The flameless heater of claim 5 wherein at least one of said locators is releasably retained in said metallic tube to releasably retain said heater assembly therein.

v9. The flameless heater of claim 5 wherein said metallic tube has circumferentially spaced re-entrant slots in one end thereof and at least one of said locators has tabs thereon engageable in said re-entrant slots to releasably retain said one locator and said heater assembly in said metallic tube.

10. The flameless heater of claim 7 wherein said metallic tube has circumferentially spaced re-entrant slots in one end thereof and said other disc has tabs thereon engageable in said re-entrant slots to releasably retain said other disc and said heater assembly in said metallic tube.

11. The flameless heater of claim 5 wherein at least one of said locators comprises a disc releasably received in said metallic tube to releasably retain said heater assembly therein.

12. The flameless heater of claim 5 wherein said metallic tube communicates with the atmosphere adjacent both ends of said porous tube of said heater assembly whereby atmospheric air may pass upwardly through said metallic tube adjacent the outer peripheral surface of said heater assembly.

13. The flameless heater of claim 1 wherein said injector comprises a tube extending into said porous tube adjacent the lower end thereof.

14. The flameless heater of claim- 1 wherein said injector comprises a first metallic tube adjacent one end of said porous tube and the flameless heater also comprises a second metallic tube closed adjacent one end and at least in part received in said porous tube adjacent the other end thereof, said first and second tubes each having an open end within said porous tube with said open ends being in spaced-apart generally opposed and generally coaxial relation to each other.

15. The flameless heater of claim 1 wherein said in- 5 jector is adjacent the upper end of said porous tube and the flameless heater also comprises an evaporator received in said porous tube adjacent the lower end thereof and underlying said injector to receive liquid fuel discharged from said injector and subsequently vaporize such liquid fuel and discharge the vaporized fuel into said porous tube.

16. The flameless heater of claim wherein said evaporator comprises a metallic tube with a closed lower end and a flared upper end adapted to funnel l'iq- 15 uid fuel discharged from said injector into the interior of said metallic tube.

17. A flameless heater using a combustible hydrocarbon fuel in liquid state for preheating liquid coolant of an internal combustion engine comprising; an elongate heat exchanger having an inlet and an outlet for liquid coolant of an engine, said heat exchanger being adapted to be mounted with its axis extending generally vertically, an elongate catalytic heater assembly received in said heat exchanger, said catalytic heater assembly comprising an elongate porous hollow tubular carrier impregnated with a catalytic material, both ends of said hollow tubular carrier being closed, an electric resistance heater element carried by said tubular carrier for preheating said catalytic material, a fuel injector at least in part received'in said hollow tubular carrier adjacent the upper end thereof for discharging at least partially vaporized hydrocarbon fuel into the interior of said hollow tubular carrier, and a fuel evapora-- tor at least in part received in said hollow tubular carrier adjacent the lower end thereof and underlying said injector to receive liquid fuel discharged from said injector and subsequently vaporize such liquid fuel and discharge the vaporized fuel into said hollow tubular carrier, whereby when vaporized hydrocarbon fuel is 40 discharged into said catalytic heater assembly when preheated by said electric resistance element, the fuel is oxidized by a flameless catalytic reaction to heat liquid coolant of the engine in the heat exchanger.

18. The flameless heater of claim 17 wherein said hollow tubular carrier comprises an elongate rigid porous tube, end caps closing both ends of said porous tube, and a fibrous material overlying said porous tube and impregnated with said catalytic material.

19. The flameless heater of claim 17 wherein said fuel injector and said fuel evaporator each comprise a metallic tube extending at least in part into said hollow tubular carrier in generally coaxial alignment with each other and each having an open end with said open ends being in spaced-apart generally opposed relation within said tubular carrier.

20. The flameless heater of claim 17 wherein said heat exchanger has a generally cylindn'cally shaped metallic tubular wall having an axial length exceeding the axial length of said hollow tubular carrier and an inside diameter exceeding the outside diameter of said hollow tubular carrier, said metallic tubular wall of said heat exchanger being in contact with liquid coolant in said heat exchanger and lying adjacent to said catalytic heater assembly, and locators carried by said metallic tubular wall of said heat exchanger adjacent opposed ends of said catalytic heater assembly to position said catalytic heater assembly generally coaxially within said metallic tubular wall of said heat exchanger.

21. The flameless heater of claim 17 wherein said evaporator comprises a metallic tube with a closed lower end adapted to receive liquid fuel discharged from said injector into the interior of said metallic tube of said evaporator.

22. A flameless heater using a combustible hydrocarbon fuel for preheating liquid coolant of an internal combustion engine comprising; an elongate heat exchanger having an inlet and an outlet for liquid coolant of an engine, said heat exchanger being adapted to be mounted with its axis extending generally vertically, an elongate catalytic heater assembly received in said heat exchanger, said catalytic heater assembly comprising an elongate porous hollow tubular carrier impregnated with a catalytic material, both ends of said hollow tubular carrier being closed, an electric resistance heater element carried by said tubular carrier for preheating said catalytic material, a first fuel injector tube at least in part received within said tubular carrier adjacent one end thereof for discharging at least partially vaporized hydrocarbon fuel into the interior of said hollow carrier, and a second tube sealed adjacent one end and at least in part received within said tubular carrier adjacent the other end thereof, said first and second tubes each having an opening within said tubular carrier and being at least in part generally coaxially aligned with said openings in spaced-apart generally opposed relation to each other, whereby when a vaporized hydrocarbon fuel is discharged by said injector into said catalytic heater assembly when preheated by said electric resistance element, the fuel is oxidized by a flameless catalytic reaction to heat liquid coolant of the engine in the heat exchanger. 

1. A flameless heater using a combustible hydrocarbon fuel for preheating liquid coolant of an internal combustion engine comprising; an elongate, cylindrically shaped heat exchanger having an inlet and an outlet for liquid coolant of an engine, said heat exchanger being adapted to be mounted with its axis extending generally vertically, an elongate catalytic heater assembly received in said cylindrically shaped heat exchanger, said catalytic heater assembly comprising an elongate porous tube, end caps closing both ends of said porous tube, a layer of fibrous material overlying said porous tube and being impregnated with a catalytic material, an electric resistance heater element carried by said porous tube for preheating said catalytic material, and a fuel injector extending into said porous tube for discharging at least parTially vaporized hydrocarbon fuel into the interior of said porous tube, whereby when a vaporized hydrocarbon fuel is discharged by said injector into said catalytic heater assembly when preheated by said electric resistance element, the fuel is oxidized by a flameless catalytic reaction to heat liquid coolant of the engine in the heat exchanger.
 2. The flameless heater of claim 1 which also comprises a temperature responsive switch mounted on one of said end caps.
 3. The flameless heater of claim 1 wherein said injector extends through one of said end caps and comprises an evaporator tube adapted to discharge at least partially vaporized hydrocarbon fuel into the interior of said tube adjacent the mid portion of the longitude of said porous tube.
 4. The flameless heater of claim 2 wherein said injector extends through one of said end caps and comprises an evaporator tube adapted to discharge at least partially vaporized hydrocarbon fuel into the interior of said porous tube adjacent the mid portion of the longitude of said porous tube.
 5. The flameless heater of claim 1 which comprises an elongate metallic tube having an axial length exceeding the axial length of said porous tube of said heater assembly and an inside diameter exceeding the outside diameter of said heater assembly, locators received in said metallic tube adjacent opposed ends of said heater assembly to position said heater assembly generally coaxially with metallic tube.
 6. The flameless heater of claim 5 wherein said metallic tube is a wall of said heat exchanger which is in contact with liquid coolant in said heat exchanger.
 7. The flameless heater of claim 5 wherein said locators comprise discs and which also comprises abutments on said metallic tube engageable with one of said discs to limit movement of said one disc generally axially through said metallic tube in at least one direction, said one disc bearing on said heater assembly adjacent one end thereof, and a spring interposed between said other disc and said heater assembly to urge said one disc into engagement with both said abutment and said heater assembly.
 8. The flameless heater of claim 5 wherein at least one of said locators is releasably retained in said metallic tube to releasably retain said heater assembly therein.
 9. The flameless heater of claim 5 wherein said metallic tube has circumferentially spaced re-entrant slots in one end thereof and at least one of said locators has tabs thereon engageable in said re-entrant slots to releasably retain said one locator and said heater assembly in said metallic tube.
 10. The flameless heater of claim 7 wherein said metallic tube has circumferentially spaced re-entrant slots in one end thereof and said other disc has tabs thereon engageable in said re-entrant slots to releasably retain said other disc and said heater assembly in said metallic tube.
 11. The flameless heater of claim 5 wherein at least one of said locators comprises a disc releasably received in said metallic tube to releasably retain said heater assembly therein.
 12. The flameless heater of claim 5 wherein said metallic tube communicates with the atmosphere adjacent both ends of said porous tube of said heater assembly whereby atmospheric air may pass upwardly through said metallic tube adjacent the outer peripheral surface of said heater assembly.
 13. The flameless heater of claim 1 wherein said injector comprises a tube extending into said porous tube adjacent the lower end thereof.
 14. The flameless heater of claim 1 wherein said injector comprises a first metallic tube adjacent one end of said porous tube and the flameless heater also comprises a second metallic tube closed adjacent one end and at least in part received in said porous tube adjacent the other end thereof, said first and second tubes each having an open end within said porous tube with said open ends being in spaced-apart generally opposed and generally coaxial relation to each other.
 15. The flameless heater of cLaim 1 wherein said injector is adjacent the upper end of said porous tube and the flameless heater also comprises an evaporator received in said porous tube adjacent the lower end thereof and underlying said injector to receive liquid fuel discharged from said injector and subsequently vaporize such liquid fuel and discharge the vaporized fuel into said porous tube.
 16. The flameless heater of claim 15 wherein said evaporator comprises a metallic tube with a closed lower end and a flared upper end adapted to funnel liquid fuel discharged from said injector into the interior of said metallic tube.
 17. A flameless heater using a combustible hydrocarbon fuel in liquid state for preheating liquid coolant of an internal combustion engine comprising; an elongate heat exchanger having an inlet and an outlet for liquid coolant of an engine, said heat exchanger being adapted to be mounted with its axis extending generally vertically, an elongate catalytic heater assembly received in said heat exchanger, said catalytic heater assembly comprising an elongate porous hollow tubular carrier impregnated with a catalytic material, both ends of said hollow tubular carrier being closed, an electric resistance heater element carried by said tubular carrier for preheating said catalytic material, a fuel injector at least in part received in said hollow tubular carrier adjacent the upper end thereof for discharging at least partially vaporized hydrocarbon fuel into the interior of said hollow tubular carrier, and a fuel evaporator at least in part received in said hollow tubular carrier adjacent the lower end thereof and underlying said injector to receive liquid fuel discharged from said injector and subsequently vaporize such liquid fuel and discharge the vaporized fuel into said hollow tubular carrier, whereby when vaporized hydrocarbon fuel is discharged into said catalytic heater assembly when preheated by said electric resistance element, the fuel is oxidized by a flameless catalytic reaction to heat liquid coolant of the engine in the heat exchanger.
 18. The flameless heater of claim 17 wherein said hollow tubular carrier comprises an elongate rigid porous tube, end caps closing both ends of said porous tube, and a fibrous material overlying said porous tube and impregnated with said catalytic material.
 19. The flameless heater of claim 17 wherein said fuel injector and said fuel evaporator each comprise a metallic tube extending at least in part into said hollow tubular carrier in generally coaxial alignment with each other and each having an open end with said open ends being in spaced-apart generally opposed relation within said tubular carrier.
 20. The flameless heater of claim 17 wherein said heat exchanger has a generally cylindrically shaped metallic tubular wall having an axial length exceeding the axial length of said hollow tubular carrier and an inside diameter exceeding the outside diameter of said hollow tubular carrier, said metallic tubular wall of said heat exchanger being in contact with liquid coolant in said heat exchanger and lying adjacent to said catalytic heater assembly, and locators carried by said metallic tubular wall of said heat exchanger adjacent opposed ends of said catalytic heater assembly to position said catalytic heater assembly generally coaxially within said metallic tubular wall of said heat exchanger.
 21. The flameless heater of claim 17 wherein said evaporator comprises a metallic tube with a closed lower end adapted to receive liquid fuel discharged from said injector into the interior of said metallic tube of said evaporator.
 22. A flameless heater using a combustible hydrocarbon fuel for preheating liquid coolant of an internal combustion engine comprising; an elongate heat exchanger having an inlet and an outlet for liquid coolant of an engine, said heat exchanger being adapted to be mounted with its axis extending generally vertically, an elongate catalytic heater assembly received in said heat exchanger, said catalytic hEater assembly comprising an elongate porous hollow tubular carrier impregnated with a catalytic material, both ends of said hollow tubular carrier being closed, an electric resistance heater element carried by said tubular carrier for preheating said catalytic material, a first fuel injector tube at least in part received within said tubular carrier adjacent one end thereof for discharging at least partially vaporized hydrocarbon fuel into the interior of said hollow carrier, and a second tube sealed adjacent one end and at least in part received within said tubular carrier adjacent the other end thereof, said first and second tubes each having an opening within said tubular carrier and being at least in part generally coaxially aligned with said openings in spaced-apart generally opposed relation to each other, whereby when a vaporized hydrocarbon fuel is discharged by said injector into said catalytic heater assembly when preheated by said electric resistance element, the fuel is oxidized by a flameless catalytic reaction to heat liquid coolant of the engine in the heat exchanger. 